The present invention relates to a solid-state imaging device. In particular, the invention concerns a solid-state imaging device which is provided with means for suppressing the phenomenon of smear.
In the imaging device for converting images into electric signals, there prevails at present a tendency for employing as a photoelectric converter element a solid-state imaging element realized through semiconductor integrated circuit technology. Owing to the use of such solid-state imaging element, the imaging device can be implemented in a much miniaturized size with lower weight and enjoy higher reliability as well as a lengthened use life when compared with the pickup-tube type imaging device.
There is shown in in FIG. 3 of the accompanying drawings of a circuit configuration of a well known solid-state imaging device. See, for example, U.S. Pat. No. 4,392,158 dated July 5, 1983 assigned to the present assignee. Referring to this Figure, it goes without saying that only the regions of photodiodes 1 should desirably exhibit the sensitivity to light. In practice, however, peripheral parts of the photodiodes such as, for example, drain regions of MOS transistors 2 connected to the vertical signal lines 3 may often have the light sensitivity. In this connection, it should be noted that all the drains of the several hundred MOS transistors arrayed in the vertical direction are connected to each of the vertical signal lines 3. Accordingly, electric charges generated photoelectrically in all the drain regions are totaled to be stored or accumulated on the vertical signal lines 3, resulting in that signal charge proportional to the amount of light integrated in the vertical direction of a projected light image is stored or accumulated on each of the vertical signal lines.
The signal charge thus accumulated is output as superposed on normal signal charge generated by the photodiodes in every horizontal scan period. For this reason, when an image of an object to be picked up has bright portions H.sub.1 and H.sub.2 with dark surroundings shown in FIG. 2a, there are produced "false signals" which correspond to vertically trailing portions H.sub.1 ' and H.sub.2 ' with enough illuminance to be visual, as shown in FIG. 2b.
The noise component peculiar to the solid-state imaging device is referred to as the vertical smear. See, for example, Japanese Patent Laid-Open No. 57-17276 laid open Feb. 1, 1982 (Japanese patatent application No. 5681085 dated July 20, 1979) assigned to the present assignee.